A METHOD FOR SIMULATING CADMIUM TRANSPORT IN SOIL - MODEL DEVELOPMENT AND EXPERIMENTAL EVALUATION

A model for simulating cadmium transport in Soil is presented. The calculation scheme is based on a three-dimensional advection-dispersion model. The adsorption process is defined by a lumped parameter mathematical model in which the, amount of ions that remains in solution is correlated with the amount that originally exists in the input solution. Desorption is defined in the same way by correlating the amount of ions desorbed with the amount of ions held by the soil solid surface. Both relationships incorporate the effect of soil solution pH, which is defined by a power equation that predicts the pH value at any time and at any depth, from the pH of the input solution and elapsed time. Soil column experiments were conducted to validate the performance of the model. Also, batch tests were employed to determine the essential adsorption-desorption parameters that are required to operate the model. In light of the results, it was concluded that the model satisfactorily forecasts cadmium concentration and the pH of soil solution under varied acidic conditions. However, values of model parameters are strictly empirical and need to be determined for each soil type.